Struct ProtocolFeatures

#[non_exhaustive]
pub struct ProtocolFeatures {
    pub rate_limit_error: Option<i32>,
    pub lwt_optimization_meta_bit_mask: Option<u32>,
    pub tablets_v1_supported: bool,
}

Which protocol extensions are supported by the server.

This is used to inform the server about the features that the client supports, so that the server can adjust its behavior accordingly.

So to draw the picture:

• server responds to an OPTIONS frame with a SUPPORTED frame with the list of protocol features it supports;
• client parses the SUPPORTED frame by extracting extensions it recognizes (supports) and creates a ProtocolFeatures instance;
• from now on, client uses this instance to determine how to handle certain frames, e.g. whether to expect a rate limit error or how to handle LWT operations;
• client also adds the features it supports to the STARTUP frame and sends it to the server, which finishes the extensions negotiation process.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

rate_limit_error: Option<i32>

The error code to use for rate limit errors, if negotiated.

lwt_optimization_meta_bit_mask: Option<u32>

The bit mask used for the LWT optimization, if negotiated. This is used to mark PREPARED response frames as related to LWT operations in order to to optimize the handling of LWT requests.

The mask is ANDed with the flags of the PREPARED response frame, and if the result is equal to the mask, it means that the frame is related to an LWT operation.

tablets_v1_supported: bool

Whether the server supports tablets routing v1.

Implementations

impl ProtocolFeatures

pub fn parse_from_supported(supported: &HashMap<String, Vec<String>>) -> Self

Parses the supported protocol features from the supported map.

pub fn add_startup_options( &self, options: &mut HashMap<Cow<'_, str>, Cow<'_, str>>, )

Adds the protocol features as STARTUP options.

pub fn prepared_flags_contain_lwt_mark(&self, flags: u32) -> bool

Checks if the given flags of a PREPARED response contain the LWT optimization mark.

If the extension was not negotiated, it conservatively returns false.

Trait Implementations

impl Clone for ProtocolFeatures

fn clone(&self) -> ProtocolFeatures

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ProtocolFeatures

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ProtocolFeatures

fn default() -> ProtocolFeatures

Returns the “default value” for a type.

impl PartialEq for ProtocolFeatures

fn eq(&self, other: &ProtocolFeatures) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for ProtocolFeatures

impl Eq for ProtocolFeatures

impl StructuralPartialEq for ProtocolFeatures